The disclosed invention relates generally to a medical device and more particularly to a ureteral stent having a temporally variable hardness.
Ureteral stents are typically placed within a urinary tract of a patient such that one end portion of the ureteral stent is located in a kidney of the patient and the other end portion of the ureteral stent is located in either a bladder or a ureter of the patient. Some known ureteral stents include retention members configured to retain the ureteral stent in a desired position within the patient. Known ureteral stents are typically positioned within the urinary tract of the patient by placing a guidewire within the patient, sliding the ureteral stent on the guidewire, and then pushing the ureteral stent along the guidewire into a desired position using a push rod. After an appropriate period of time, the ureteral stent is removed from the patient, for example by pulling the ureteral stent from the urinary tract of the patient.
Known ureteral stents are designed to provide optimal functionality while minimizing patient discomfort. Some design features that provide improved comfort, however, may decrease functionality. For example, hard stents are known to be more resistant to deformation and easier to position within the urinary tract than soft stents. As the hardness of the stent increases, however, the patient will generally experience greater discomfort while the stent is within the urinary tract. Conversely, softer stents may alleviate patient discomfort, but they are generally more difficult to insert into the patient.
To accommodate the need for both comfort and functionality, some known ureteral stents are configured such the stent hardness (also characterized as the stent durometer) varies spatially along the longitudinal axis of the stent. For example, the distal end section has a relatively high durometer, facilitating insertion of the stent (for which the durometer of the distal end portion is more important) while the proximal end portion has a relatively low durometer, affording greater comfort to the patient because the proximal end portion is typically in contact with the more sensitive area at the junction of the ureter and bladder. Other known stents are configured such that all or a portion of the stent dissolves or degrades upon being inserted into the patient's urinary tract, thereby increasing patient comfort and eliminating the need to remove the stent. Such dissolvable stents, however, do not retain their original shape or size.
Thus, a need exists for a ureteral stent configured to have a relatively high durometer to ease insertion and that softens after insertion to increase patent comfort, while retaining its original size and/or shape.